An implantable medical device (IMD), such as a cardiac pacemaker or a cardioverter-defibrillator, provides therapeutic electrical stimulation to a patient via electrodes carried by one or more implantable leads. The IMD may provide the electrical stimulation based on sensed physiological parameters of the patient, such as sensed electrical signals via electrodes carried by the implantable leads.
The IMD may detect various types of arrhythmias based on the electrical signals sensed by the IMD. For example, the IMD may detect ventricular tachycardia (VT) or ventricular fibrillation (VF) based on sensed electrical signals. The IMD may provide various electrical therapies in response to detection of VT/VF. Specifically, the IMD may provide one or more defibrillation shocks in response to detection of VT/VF. Additionally, the IMD may provide antitachycardia pacing (ATP) in response to detection of VT in order to remedy the VT before it progresses to VF.
However, identification of VT/VF by the IMD may be subject to error. For example, the IMD may inappropriately characterize a supraventricular tachycardia (SVT) as VT/VF. Also, the IMD may mistakenly detect VT/VF due to oversensing or undersensing. Misidentification of VT/VF due to SVTs, oversensing, or undersensing may result in inappropriate application of electrical therapy by the IMD. Specifically, the IMD may unnecessarily provide a defibrillation shock based on a misidentification of VT/VF due to SVTs, oversensing, or undersensing.
IMDs may store electrogram waveforms (EGMs) that represent the electrical activity of the heart that resulted in identification of the tachyarrhythmia by the IMD and delivery of electrical therapy (e.g., defibrillation shocks). Clinicians may download and review the stored EGMs, marker channel data, and other data to determine whether the electrical therapy was appropriately/inappropriately applied. The clinicians may make the determination based on a characterization of the stored EGM and a type of electrical therapy applied. For example, a clinician may determine that a defibrillation shock was inappropriately applied if the clinician characterizes the EGM associated with the defibrillation shock as representing an SVT or including oversensing or undersensing, since these conditions may not necessitate a defibrillation shock. A clinician may determine that a defibrillation shock was appropriately applied if the clinician characterizes the EGM associated with the defibrillation shock as VT/VF, since these conditions may require a defibrillation shock.